Historically, the sitting cushion used in meditation—called a zafu—has been round and low, frequently having dimensions of approximately 7 inches high and 16 inches in diameter. The traditional filling in zafus is kapok, a natural fiber obtained from Kapok tree seedpods. In the 2500 year history of meditation cushions, traditionally a meditation cushion is a single composite of cushioning material within an outer cover, not a cushion of layered materials.
A person mediating would typically be seated in a cross-legged fashion on zafu sitting cushion. In these postures, the legs are crossed or folded in front of the sitter in what is called “lotus posture” or one of its variations. The meditator's knees can rest on the floor and the cushion supports his or her sit bones. Alternatively, meditators use a kneeling posture called seiza. In this kneeling posture, the person's weight and bones which contact the cushion are again supported (by the cushion) which the meditator straddles.
Under the cushion is a meditation mat called zabuton. The typical measurements for such mats is approximately 32″ by 27″ and 3-6″ high. A traditional mat has cotton batting contained in a seamed natural or synthetic cover. The zabu ton provides the meditator with a kind of “pillow” for the legs, giving some added support, warmth, and protection from the hard floor underneath. With prolonged use, the mat will eventually compress, becoming thin and less able to support the meditator's weight in a comfortable manner. Even when the mat is new and full, it lacks the ability to accommodate to the specific body weight of the meditator without over compressing, which results in the meditator's knees pressing against the hard floor.
Mediation cushions of kapok have commonly noted problems associated with their use.
There are two main reasons why sitting in meditation causes physical pain: First, the sitting bones are not elevated at the proper height. When the height isn't right for the individual, there is stress on knees and/or ankles that causes pain. Both too-high seats and too-low seats cause problems. In general, the more flexible an individual is, the lower the seat can be without causing difficulty.
Second, the sitting cushion is too hard. In this case the unforgiving material pressed against the buttocks blocks circulation, presses on nerves and causes discomfort and pain or complete loss of feeling.
The traditional material for meditation cushions is kapok. An individual kapok cushion can be adjusted for height and firmness by added or removing material. However, there is a limit due to the compressibility of the kapok itself. If a relatively high seat is required (as when the meditator has limited flexibility in hips and knees) the amount of kapok need to achieve that height is so great that it produces a seat that is extremely firm. The firm seat causes a problem because it is too hard.
This is the sitting cushion dilemma. If the cushion is stiff enough to give enough lift, it is also likely to cause pressure problems because of that very stiffness.
With buckwheat hulls it is possible to achieve greater lift with much less material, because the material does not compress. At the same time, as with a fully stuffed kapok cushion, a buckwheat hull seat is very hard and causes discomfort when used for extended periods.
Typically meditators deal with these limitations by shifting back and forth among imperfect alternatives, since difficulties usually take a few sitting periods to become extreme. Up until now the only other solution (which is not available to all) is to increase flexibility or lose weight to the point where a relatively soft kapok cushion is adequate to achieve a comfortable height.
Kapok-filled cushions are very firm initially, and soften gradually over time. Both the initial firmness and the long-term softness present physical difficulties for meditators. A new kapok cushion is usually too hard for most meditators. Its firmness frequently results in numbness to the legs and genitals lasting for the duration of the meditation period, and sometimes beyond. As the cushion softens, it loses its ‘loft’ and begins to sink. This results in a softer but lower cushion, which can cause additional strain on the bent knees and back from a lower than comfortable position. Although additional kapok can be added to the cushion, kapok does present certain hazards during handling. The fine cotton-like strands can be irritating when inhaled and thus necessitate the use of a mask when handling kapok.
Most significantly, the ever-changing nature of kapok leads to a constant variation in cushion density and height, which in turn results in less than consistent comfort for the meditator. Common complaints associated with the use of kapok-filled cushions include: back pain, knee pain (due to cushions that are either too high or too low), pain over the sacrum (tail bone) from pressure of the unyielding cushion, and numbness in the legs or genital area due to pressure on the sciatic nerve or other nerves running near the ‘sit bones’ that bear the weight in meditating.
Sitting cushions sometimes contain only buckwheat hulls and also generate common problems associated with physical discomfort, particularly numbness in the legs where the edge of the bucket-filled cushion contacts the sciatic nerve area under the buttock. In addition, pain in the sacral area or on the ‘sit bones’ themselves commonly occurs due to the unyielding nature of the buckwheat hulls. The buckwheat hulls, while having some ability to shift and ‘hold’ the weight of the person's buttocks, are a virtually incompressible material and thus ‘push back’ onto the offered weight, frequently creating discomfort.
Meditators typically sit completely motionless for some time, often approximately from 20 minutes to an hour. During longer retreats held periodically at meditation or religious centers and/or monasteries, meditators may sit for twelve or more 35-minute periods per day. Physical discomfort, which at times can be significant, frequently appears. The pain associated with meditation is most commonly present in the knees, ankles, hips, back and neck, and older meditators are particularly susceptible to it. However, younger people also have limitations such as previous injuries, arthritis, and/or chronic illness which create pain while sitting still for long periods of time. In addition, there is the general stiffness and discomfort that are the natural result of sitting still in one position over long periods of time. Lastly, meditating at all is difficult for some people, especially if they are unable to find a cushion and mat that will allow them to participate in the meditation sessions comfortably, without having to bear significant pain. For these reasons, there is at present a real need for a meditation cushion and mat that alleviate the discomfort associated with seated meditation.